An interior body of a disposable diaper includes a liquid-permeable front sheet, a liquid-impermeable back sheet and a liquid-retaining absorbent core. The front sheet has a single sheet including spunbond layers on the front side and back side and a melt blown layer between the spunbond layers. The absorbent core has fiber aggregates and super-absorbent polymer particles. The front sheet is directly bonded to the skin side surface of the absorbent core. The length of the front sheet is longer than the length of the absorbent core, so that the front sheet has extended sections which extend outward in the lengthwise direction from both ends of the absorbent core in the lengthwise direction, while the extended sections are each continuously connected in the transverse direction with the front sheet or back sheet which overlaps with the extended section. The extended sections can directly contact the skin of the wearer.
|
1. An absorbent article comprising a liquid-permeable front sheet, a liquid-impermeable back sheet and a liquid-retaining absorbent core, wherein
the front sheet consists of a single laminated sheet comprising spunbond layers on front and back sides and at least one melt blown layer between the spunbond layers, wherein the spunbond layer on the front side has a pattern embossed surface, and the spunbond layer on the back side has a flat embossed surface,
the absorbent core consists of fiber aggregates and super-absorbent polymer particles,
the front sheet covers a skin side surface of the absorbent core while being directly bonded to the skin side surface,
the length of the front sheet in a lengthwise direction of the absorbent article is longer than the length of the absorbent core in the lengthwise direction so that the front sheet is provided with extended sections which extend outward in the lengthwise direction from both ends in the lengthwise direction of the absorbent core, the extended sections being each continuously connected in a transverse direction of the absorbent article with the front sheet or back sheet which overlaps with the extended section,
the extended sections are adapted to contact the skin of a wearer,
the spunbond layer on the front side is directly contactable with the skin of the wearer,
the spunbond layer on the back side is in direct contact with at least one of the fiber aggregates or super-absorbent polymer particles on the skin side surface of the absorbent core, and
a fiber density of the spunbond layer on the back side is higher than that of the spunbond layer on the front side.
2. An absorbent article according to
the liquid diffusibility of the front sheet is at least 20 mm by a Klemm water absorption test, and
the weight ratio of the super-absorbent polymer particles in the absorbent core is no greater than 40 percent.
3. An absorbent article according to
4. An absorbent article according to
5. An absorbent article according to
6. An absorbent article according to
7. An absorbent article according to
8. An absorbent article according to
9. An absorbent article according to
10. An absorptive article according to
both the spunbond layer on the back side and the spunbond layer on the front side have fiber orientations in the lengthwise direction.
11. An absorptive article according to
the spunbond layer on the front side includes high-compression regions, in which fibers are contact-bonded together, and low-compression regions, in which the fibers are essentially not contact-bonded together, and
the spunbond layer on the back side is essentially evenly compressed in overall.
|
The present application is a National Phase of International Application Number PCT/JP2011/072705, filed Sep. 26, 2011, and claims priority from Japanese Application Number 2010-223096, filed Sep. 30, 2010.
The present invention (disclosure) relates to an absorbent article.
In the prior art there are known absorbent articles, such as disposable diapers, that comprise a liquid-permeable front sheet, a liquid-impermeable back sheet, a liquid-retaining absorbent core and a core wrap surrounding the absorbent core (see PTL 1).
PTL 1: U.S. Pat. No. 5,458,592
Incidentally, the number of disposable diapers in use in developing countries is still low compared to developed countries. This is believed due to the high cost of diapers for people living in developing countries. For provision of diapers at low cost, therefore, it is necessary to significantly reduce the production cost of diapers.
Significant reduction in production cost will require a major change, for example, in construction to eliminate parts commonly provided in diapers for advanced countries. However, a construction which reduces a production cost significantly is not disclosed in PTL 1.
According to the present invention there is provided an absorbent article comprising a liquid-permeable front sheet, a liquid-impermeable back sheet and a liquid-retaining absorbent core, wherein the front sheet consists of a single sheet comprising spunbond layers on the front side and back side and a melt blown layer between the spunbond layers, the absorbent core consists of fiber aggregates and super-absorbent polymer particles, the front sheet covers the skin side surface of the absorbent core while being directly bonded to the skin side surface, the length of the front sheet in the lengthwise direction is longer than the length of the absorbent core in the lengthwise direction so that the front sheet is provided with extended sections which extend outward in the lengthwise direction from both ends in the lengthwise direction of the absorbent core, the extended sections being each continuously connected (joined together) in the transverse direction with the front sheet or back sheet which overlaps with the extended section, and the extended sections can be contacted with the skin of a wearer.
It is possible to greatly reduce production cost of absorbent articles without significantly reducing function.
The inventor(s) has/have recognized that significant reduction in production cost is possible when one or more parts commonly provided in diapers for developed countries is/are eliminated. If, for example, the front sheet is arranged to perform the added function of surrounding the absorption core, this would allow the core wrap to be eliminated, thereby allowing production cost to be greatly reduced without notably reducing functionality.
The present invention may be applied to a disposable diaper comprising an interior body and an exterior body (also referred to as chassis or outer cover). Alternatively, the present invention may also be applied to other absorbent (absorptive) articles such as sanitary napkins, panty liners and incontinence pads.
Referring to
The front sheet 2 consists of a single sheet, preferably in a rectangular shape, and may comprise, for example, spunbond layers on the front side (also referred to as skin side) and back side (also referred to as non-skin side), and a melt blown layer between the spunbond layers. In a preferred case, the basis weight of the entire front sheet 2 may be about, for example, 10 g/m2, the basis weight of both the spunbond layers may be about, for example, 8 g/m2 and the basis weight of the melt blown layer may be about, for example, 2 g/m2. The melt blown layer may also be coated with a hydrophilic lubricant.
The single sheet of the front sheet 2 may be a laminated sheet formed by stacking the front side and back side spunbond layers with the melt blown layer in between, and then pattern embossing the front side spunbond layer while flat embossing the back side spunbond layer. In the pattern embossing and flat embossing, the fibers inside the front sheet 2 are contact bonded while being heated. The pattern embossing is carried out using an embossing tool having a patterned indented surface, while the flat embossing is carried out using an embossing tool having a flat surface.
The two spunbond layers of the front sheet 2 preferably have a fiber orientation in the lengthwise direction. The fiber orientation of the sheet can be determined based on the tensile strength of the sheet, for example. That is, samples are prepared along the lengthwise direction and the transverse direction of the sheet, and the tensile strength under constant stretching is measured using a tensile tester (Shimadzu Corp., Autograph). When the tensile strength of the sample along the lengthwise direction is larger than the tensile strength of the sample along the transverse direction, the fiber orientation is judged to be along the lengthwise direction.
The front sheet 2 preferably has a liquid diffusibility of, for example, at least 20 mm based on a Klemm water absorption test (JIS-L1907, P8141).
The Klemm water absorption test can be carried out in the following manner. Specifically, a sample having a width of 15 mm and a length of 100 mm is prepared, and is suspended vertically using a suspender. The lower end part of the sample having a 15 mm length is then immersed in the distilled water, and is kept there for 10 minutes. After that, the height of water ascending through the sample by capillary action is measured. The test is carried out at a temperature of 20±1° C.
In addition, the tensile strength in the lengthwise direction and the tensile strength in the transverse direction of the front sheet 2 are each preferably at least 4.0 N/25 mm, both when dry and when wet. It is confirmed that such tensile strengths prevent the front sheet from being torn when the load is applied to the front sheet due to the movement of the wearer.
The tensile strength (N/25 mm) can be measured in the following manner. Specifically, a test sample having a width of 25 mm and a length of 50 mm is prepared. In more detail, when measuring the tensile strength in the lengthwise direction, the sample is prepared so that the lengthwise direction of the sample extends in the lengthwise direction of the diaper. When measuring the tensile strength in the width direction, the sample is prepared so that the lengthwise direction of the sample extends in the width direction of the diaper. The tensile strength of the sample is then measured using a tensile tester (Shimadzu Corp., Type AG-50NI). That is, the sample is stretched by 100 mm/min until the sample is broken. The maximum strength of the sample during the measurement is determined as the tensile strength of the sample.
The tensile strength of the sample when dry is measured using a dry sample. The tensile strength of the sample when wet is measured using a wet sample. The wet sample is obtained by putting drops of distilled water onto the sample until the distilled water penetrates the entire sample.
The back sheet 3 preferably has a rectangular shape, and is composed of, for example, a hydrophobic nonwoven fabric, an impermeable plastic film, or a laminated sheet comprising a nonwoven fabric and an impermeable plastic film. The back sheet 3 may be either air permeable or non-air permeable.
The absorbent core 4 preferably comprises broad sections at both ends in the lengthwise direction, and a narrow section in the middle between the broad sections, and consists of fiber aggregates and super-absorbent polymer particles. The fiber aggregates may comprise, for example, cellulose-based fibers such as pulp fiber, cotton fiber or rayon fiber, or synthetic fiber composed of a polyester/polyethylene-based synthetic resin. The super-absorbent polymer (SAP) particles may comprise, for example, an acrylic acid-based polymer or copolymer that gels by retention of liquid, and are preferably capable of absorbing and retaining liquid in an amount of over 15 times their own weight.
The weight ratio of the SAP particles in the absorbent core 4, i.e. the ratio of the weight of the SAP particles with respect to the total weight of the absorbent core 4 (which is the total weight of the fiber aggregate weight plus the SAP particle weight) is preferably no greater than 40 percent, for example.
The SAP particle weight ratio is calculated in the following manner. Specifically, 1 g each of the SAP sample and fiber sample is collected from the product to be measured (the absorbent core 4 is loosened, and the SAP and fibers are collected while using a magnifying glass or the like). Next, the collected SAP sample and fiber sample are placed in separate 250 mesh nylon bags to form test samples, and the water capacity of each is measured. The water capacity is calculated in the following manner. Specifically, the test sample is immersed in 500 ml of physiological saline for 30 minutes and then dewatered for 2 minutes at 150 G using a centrifugal separator, and the weight of the dewatered test sample is measured. The following formula is used to calculate the water capacity (g/g) of the SAP sample and the water capacity (g/g) of the fiber sample.
Water capacity(g/g) of the SAP or fiber sample=(weight of the test sample after dewatering−weight of nylon mesh−weight of the SAP or fiber sample before immersing−residual liquid weight of nylon mesh)/(weight of the SAP or fiber sample before immersing)
For this example, the weight of each of the SAP and fiber samples before immersing was 1 g.
Next, a 50 mm×50 mm absorbent core sample is prepared from the product to be measured (the size of the absorbent core sample may vary depending on the size of the product, but should be prepared as large as possible). The weight of the entire absorbent core sample T (g) is then measured.
The absorbent core sample is then placed in a 250 mesh nylon mesh bag to form a test sample and immersed for 30 minutes in 500 ml of physiological saline, after which it is dewatered for 10 minutes at 150 G using a centrifugal separator, and the weight of the dewatered test sample is measured and the water capacity of the absorbent core sample is determined.
If the SAP weight of the absorbent core sample is represented as S (g) and the fiber weight as P (g) (T=S+P), the following equation applies.
Water capacity of absorbent core sample(g)=water capacity of SAP sample(g/g)×S(g)+water capacity of fiber sample(g/g)×(T−S)(g)
The SAP weight S is calculated by the formula specified above. The following formula is then used to calculate the SAP particle weight ratio.
SAP particle weight ratio(%)=S/T
As shown in
At the intermediate section between the two extended sections 2E, as shown in
In this example, the skin side section 2S of the front sheet 2 and the skin side surface 4S of the absorbent core 4 are bonded together by a hot-melt adhesive 5S, and the non-skin side section 2NS of the front sheet 2 and the non-skin side surface 4NS of the absorbent core 4 are bonded together by a hot-melt adhesive 5NS. As a result, the liquid to be absorbed, that is inside the front sheet 2, can be rapidly transferred to the absorbent core 4.
The non-skin side section 2NS of the front sheet 2 is preferably also bonded together with the back sheet 3 by a hot-melt adhesive 6. Here, the hot-melt adhesive 6 is continuously applied in the lengthwise direction and transverse direction, so that the front sheet 2 is continuously connected (joined) to the back sheet 3 in the lengthwise direction and transverse direction.
At the extended sections 2E, as shown in
As a result, the absorbent core 4, and especially the SAP particles, are securely enveloped inside the interior body 1, so that leakage of the SAP particles out from the interior body 1 is suppressed.
That is, the front sheet 2 also functions as a core wrap surrounding the absorbent core 4. Therefore, the core wrap and second sheet can be eliminated, thus allowing the production cost of the diaper to be greatly reduced.
In this case, the front sheet 2 has sufficient tensile strength in both the lengthwise direction and the transverse direction, both when dry and when wet. Consequently, leaking out of the absorbent core 4, and especially the SAP particles, can be reliably suppressed even with elimination of the core wrap.
In addition, since the front sheet 2 includes a melt blown layer, leaking out of the SAP particles is even more reliably suppressed. At the same time, the spunbond layer on the front side of the front sheet 2 comes in contact with the skin of the wearer in use, and as a result, a satisfactory feel on the skin is obtained. Handling is also facilitated since the front sheet 2 comprises a spunbond/melt blown/spunbond three-layer structure.
Furthermore, since the spunbond layer on the front side of the front sheet 2 is pattern embossed, high-compression regions, in which the fibers are contact bonded together, and low-compression regions, in which the fibers are essentially not contact bonded together, are formed in said spunbond layer on the front side. Since the degree of freedom of the fibers is relatively high in the low-compression regions, liquids to be absorbed, such as urine, can be easily drawn into the front sheet 2.
On the other hand, since the spunbond layer on the back side of the front sheet 2 is flat embossed, the spunbond layer on the back side is essentially evenly compressed in overall. The strength of the spunbond layer on the back side (which comes in direct contact with the absorption core 4) is thereby increased, and therefore damage to the front sheet 2 by the absorbent core 4 and especially the SAP particles, is suppressed. Also, the high fiber density of the flat embossed spunbond layer on the back side suppresses the SAP particles from passing through the front sheet 2 and leaking out from the absorbent core 4.
Moreover, because the fiber density of the spunbond layer on the back side is higher than that of the spunbond layer on the front side, liquid diffusion from the spunbond layer on the front side to the spunbond layer on the back side is accelerated. In addition, since the two spunbond layers each have fiber orientation in the lengthwise direction, liquid diffusion in the lengthwise direction is accelerated.
A front sheet 2 of an exemplary embodiment of the present invention (spunbond layer: 4 g/m2 on the front side, spunbond layer: 4 g/m2 on the back side, melt blown layer: 2 g/m2 between the two spunbond layers) was subjected to a Klemm water absorption test, through which it was found that the liquid diffusibility in the lengthwise direction was 20 to 30 mm while the liquid diffusibility in the transverse direction was 5 to 15 mm. Thus, the front sheet 2 has high liquid diffusibility even though it is a simple sheet.
It should be noted that an ordinary top sheet (polyethylene/polypropylene fiber spunbond, 20 g/m2) to be contacted with a wearer's skin has the liquid diffusibility in the lengthwise direction was 10 to 15 mm and the liquid diffusibility in the transverse direction was 5 to 15 mm. In contrast, the liquid diffusibility of an ordinary tissue sheet used as the sheet surrounding an absorbent core is 25 to 35 mm in both the lengthwise direction and the transverse direction.
Furthermore, leaking out of the SAP particles can be suppressed with a SAP particle weight ratio of no greater than 40 percent. With a higher SAP particle weight ratios, the fiber aggregates may not be able to contain SAP particles inside, and the front sheet 2 may be damaged by movement of the wearer, increasing the possibility of leaking out of the SAP particles.
This has been confirmed experimentally. The experiment was conducted in the following manner. Specifically, several absorbers, each of which is defined as an absorbent core 4 surrounded by a front sheet 2, were prepared with different SAP particle weight ratios. The SAP particle weight ratio of the absorbers were 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% and 60%. The absorbent cores, absorbent core wrap sheets and front sheets were removed from commercial diapers (trade name: MoonyMan, L-size), and the absorbers were attached to the remainders of the commercial diapers to prepare diaper samples.
Five L-size users were first asked to wear black fabric underpants. This was to allow leaked off SAP particles to be easily confirmed, without adhesion of the leaked SAP particles onto the skin of the user. The users were then asked to wear the prepared diaper samples. After this, the users were allowed free activity for 30 minutes, including movements of sleeping posture, standing, running, walking and sitting. Next, 80 ml of physiological saline was absorbed into the absorber of each diaper sample, and the users were allowed activity for 30 minutes in the same manner. The presence or absence of SAP particles on the surface of the diaper and the fabric underpants surfaces was then confirmed.
No leaking out of SAP particles occurred with a SAP particle weight ratios of up to 40%. With a SAP particle weight ratio of 45%, the SAP leaked out in 2 of the 5 users.
The diaper 10 shown in
The back sheet 3 of the interior body 1 is bonded to the abdominal side section 11F and the dorsal side section 11R of the exterior body 11 at its ends in the lengthwise direction. The flank section 13F of the abdominal side section 11F and the flank section 13R of the dorsal side section 11R may be bonded together, thereby forming a “pants diaper”.
The abdominal side section 11F and the dorsal side section 11R each have a plurality of elastic members 12F and 12R extending parallel to each other in the transverse direction, and integrated in a stretched state.
Elastic member parts 12FE, 12RE of the elastic members 12F, 12R overlap the extended sections 2E of the interior body 1. As a result, the extended sections 2E contract in the transverse direction during wear, so that leaking out of the SAP particles through the extended sections 2E is further suppressed.
In addition, there is no sheet covering the extended sections 2E, and therefore the extended sections 2E can directly contact the skin of the wearer. It is thus possible to increase the absorption area of the diaper.
In
In the second embodiment of the present invention exemplarily illustrated in
In the third embodiment of the present invention exemplarily illustrated in
The fourth embodiment of the present invention exemplarily illustrated in
The fifth embodiment of the present invention exemplarily illustrated in
In the sixth embodiment of the present invention exemplarily illustrated in
In some embodiments, the front sheet 2 may consist of a single sheet which is a laminated sheet of spunbond layers on the front side and back side, and two melt blown layers between the spunbond layers. This will allow leaking out of the SAP particles to be even more reliably suppressed.
This application claims the benefit of Japanese Application No. 2010-223096 the entire disclosure of which is incorporated by reference herein.
The present invention is also defined by the following non-limiting features Ea to Eq, E1 to E13, and U1 to U15, which are not specific to the detailed embodiments described above:
a liquid-permeable front sheet, or top sheet;
a liquid-impermeable back sheet; and
a liquid-retaining absorbent core;
wherein:
the front sheet consists of a single sheet comprising spunbond layers on the front side and back side and a melt blown layer between the spunbond layers;
the absorbent core consists of fiber aggregates and super-absorbent polymer particles;
the front sheet covers the skin side surface of the absorbent core and is directly bonded thereto;
the length of the front sheet, and optionally the back sheet and/or another sheet which is an optional additional sheet provided only on the non-skin side surface of the absorbent core, in the lengthwise direction is longer than the length of the absorbent core in the lengthwise direction so as to provide extended sections which extend outward from both ends of the absorbent core in the lengthwise direction;
the components of said extended sections being continuously joined together in the transverse direction; and
the extended sections being adapted for contacting the skin of a wearer.
the front sheet is formed by laminating the front side and back side spunbond layers and the melt blown layer and then pattern embossing the spunbond layer on the front side while flat embossing the spunbond layer on the back side.
Yoshioka, Toshiyasu, Masaki, Shunsuke
Patent | Priority | Assignee | Title |
Patent | Priority | Assignee | Title |
5458592, | Jun 30 1994 | Kimberly-Clark Worldwide, Inc | Thermoplastic fibrous nonwoven webs for use as core wraps in absorbent articles |
6102892, | Dec 23 1996 | Kimberly-Clark Worldwide, Inc | Diaper with pleats for containment of liquid and solid waste |
20050033255, | |||
20060069368, | |||
20080021426, | |||
20080286320, | |||
20100217216, | |||
20110118690, | |||
EP1064893, | |||
EP2087871, | |||
JP2002119539, | |||
JP20057188, | |||
JP2008178682, | |||
JP2009106666, | |||
JP2009178384, | |||
JP3594099, | |||
JP4526323, | |||
JP9164164, | |||
WO2007032710, | |||
WO2008067184, |
Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
Sep 26 2011 | UNICHARM CORPORATION | (assignment on the face of the patent) | / | |||
Jan 18 2013 | YOSHIOKA, TOSHIYASU | UNICHARM CORPORATION | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 036755 | /0109 | |
Jan 18 2013 | MASAKI, SHUNSUKE | UNICHARM CORPORATION | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 036755 | /0109 |
Date | Maintenance Fee Events |
Jul 22 2019 | REM: Maintenance Fee Reminder Mailed. |
Jan 06 2020 | EXP: Patent Expired for Failure to Pay Maintenance Fees. |
Date | Maintenance Schedule |
Dec 01 2018 | 4 years fee payment window open |
Jun 01 2019 | 6 months grace period start (w surcharge) |
Dec 01 2019 | patent expiry (for year 4) |
Dec 01 2021 | 2 years to revive unintentionally abandoned end. (for year 4) |
Dec 01 2022 | 8 years fee payment window open |
Jun 01 2023 | 6 months grace period start (w surcharge) |
Dec 01 2023 | patent expiry (for year 8) |
Dec 01 2025 | 2 years to revive unintentionally abandoned end. (for year 8) |
Dec 01 2026 | 12 years fee payment window open |
Jun 01 2027 | 6 months grace period start (w surcharge) |
Dec 01 2027 | patent expiry (for year 12) |
Dec 01 2029 | 2 years to revive unintentionally abandoned end. (for year 12) |